The economy was going fine under Bush until the Democrats took over both the Senate and the House his last few years. Then the Democrats were in charge of spending and had control of the banks. The mortgage banking crash can be directly tied to Frank. Obama had both the sides of Congress democratic his first two years and he did absolutely nothing when he could have passed anything he wanted.
That was not due to the Obama administration, banks had been loaning out money while having high leverage to many customers with a high chance of default. Then the property boom ended, banks could not cover the bad loans, and the 2008 global financial crisis started.
One of the reason for this was that the credit rating agencies were classifying high-risk loans as very low risk in order to make greater profits for them and the banks. They also classified companies with very high leverage as being low-risk and having the best ratings possible.
Another reason is that the regulators often still held shares in some of the largest banks and had worked for them, so the regulations were made to suit the banks or at least heavily swayed by their arguments. This is still a problem as well as the effects of lobbying.
